Lesson 2: Fundamental Concepts of Environmental Geology
This week we'll explore five overarching concepts—from population growth and geologic hazards to sustainability and the unity of environmental systems—that Keller suggests provide a framework
for understanding how humans interact with Earth (as seen, at right, by the crew of Apollo XVI). Because these are very
broad concepts I would like you to think carefully about how you might apply them to understand different aspects of a specific problem. For example, the availability of fresh water is likely to become a critical issue here in California during the coming decades. How the state's citizens address this issue will depend on population growth, how the timing and amount of precipitation shift in response to global climate change, how we use and recycle water to make existing supplies sustainable, and so on. Just this one problem touches on all the key concepts Keller discusses, and in the future it will be our ability to analyze such problems holistically that will give us the best chance of making critical societal changes.
In addition to introducing the five overarching concepts mentioned above, Keller uses this first chapter to "slip in" discussions of a number of other related ideas—from geologic time to the precautionary principle—that will inform topics we'll study later. Of these "secondary" topics I would like you to pay particular attention: exponential change, which enables us to understand both population growth and geologic dating; and the scientific method, which provides a framework for developing and testing objective models of how nature operates.
Weekly Learning Objectives
Upon successful completion of this week's lesson, a student is expected to be able to:
- Apply the fundamental concepts that underlie the discipline of Environmental Geology (human population growth; sustainability; interrelatedness of Earth's systems; ubiquity of geologic hazards; and interplay between scientific knowledge and values) to (1) recognize constraints Earth imposes on specific human activities; and (2) evaluate proposed solutions to environmental problems.
- Use an understanding of exponential change to estimate: (1) the doubling time of a human population given its annual growth rate; and (2) the radiometric age of a sample given the fraction of parent element it still contains and this element's half-life.
- Outline the steps he or she would follow to investigate a geologic question using the scientific method.
Reading and Browsing Assignment
- Read Chapter 1, focusing on the both the basics of the five major concepts the author presents and how they can be used to recognize the limits Earth places on humanity and its activities. Also, be sure that you understand the key supporting principles (such as input-output analysis, uniformitarianism, carrying capacity, the precautionary principle) that the author describes as part of his introduction. In the cases of principles for which potential solutions exist (e.g., human population growth and sustainability) be sure that you can explain which solutions are generally thought to be "best" and why. Also, in order to gain a better sense of how the major concepts relate to what we're going to be learning throughout the rest of the semester you might want to look at a few of the summaries in which the author revisits these concepts at the ends of later chapters (e.g., p. 165, 360, 462, etc.).
- Read Appendix D on "How Geologists Determine Geologic Time" (p. D2-D4). Focus on understanding how the fraction of a radioactive parent element remaining in a mineral changes as the sample ages, and how this change can be used to determine the radiometric age of the sample if we know the element's half-life.
Exercise 2: Radiometric Dating (Due by 9:00 AM on 29-Aug-2011)
In this week's lesson you have learned how exponential change can be used to model the growth of human populations and the decay of radioactive elements. This week's exercise will help you learn more about how radioactive decay is used to date geologic events so that we can reconstruct Earth's history (p. 9-12) and estimate the rates of geologic processes (p. 32).
- Point your browser to the Virtual Courseware exercise on Rb-Sr dating. This program uses Java applets, so be patient as you load the intractive graphics if you are using a dial-up connection. You don't want to crash the program by trying to use the applets before they are fully loaded. Also, allow enough time to do this entire exercise in one session (about 1 hour) because, unfortunately, this program will not allow you to save your work and come back later.
- Work through the exercise by carefully reading each part of the text and then answering the accompanying questions. Don't worry if you get an answer wrong at first; the program will tell you it's wrong and give you a chance to fix it. You should take notes on key points as you work through this exercise so that you will be able to remember what you did later. Focus on understanding the basics of the decay process and don't worry too much about the details of the isochron method. (Hint: On screen 14, remember that one billion years equals 1,000 million years.)
- When you get to the end of the exercise, fill in your name, school (College of the Siskiyous) and address and press enter to see your "Virtual Geochronologist" certificate. Right-click on the blue part of the certificate, choose Copy Image, and paste it into whichever program you use to view graphics files (Windows Picture Viewer, Paintshop Pro, Photoshop, etc.). From there, save it as a graphics file (.jpg is best but .gif and .bmp work too). Be sure to remember where you saved the image and what you called it! You should view it to be sure that it saved correctly before you close or navigate away from the browser window that displays the certificate.
- Log on to the Etudes site, click on the "Assignments, Tasks and Tests" tool, and click the link for Exercise 2. Attach your certificate by using the "Browse..." button on the page and then selecting the name of the file you saved your certificate as. Finally, press the "Upload" button. This exercise is worth 10 points, and scores will be posted in the gradebook shortly after 29-Aug.
Quiz 2: Concepts of Environmental Geology (Due by 9:00 AM on 29-Aug-2011.)
Complete Quiz 2 in the ETUDES under the "Assignments, Tasks and Tests" tool. There are ten questions, each worth one point. If you can answer all of them correctly it means that you've got a pretty good handle on the concepts that will frame our study of environmental geology this semester, and are ready to start learning about plate tectonics next week. Note that like all of our weekly quizzes, this one is timed (you have 30 minutes) and must be completed in one "sitting" (that is, you will only be granted access once.) So, be sure you're ready to complete your quiz when you start it. Good luck, and don't forget to use Firefox.